How to create WAR file.

I created WAR file in MyEclipse and deployed in WebSphere Application Server 6.0 (WAS) successfully. I want to create WAR file in Eclipse and want to deploy in WAS 6.0. Is there any plugin for WAR creation in Eclipse. I created WAR file by standard command jar -cvf HelloWorld.war * But this WAR file doesn't deploy in WAS 6.0. Errors.